CT (Computed Tomography) is the abbreviation of computer tomography technology. Its imaging principle is as follows: using x-ray beam and x-ray detector of high sensitivity, a part of one person is scanned around by serial slices tomography, the x-ray penetrating the slice of the person is received by scintillator in the x-ray detector, after being converted to visible light, is converted to electric signals by photoelectric conversion device, and is then amplified and converted to digital signals by A/D conversion so as to be processed by a computer. In the computer, the selected slice is divided into a number of boxes of same volume, called a voxel. Information from the serial slices tomography is calculated to get x-ray attenuation coefficients for each voxel, or absorption coefficient for each voxel, which are then arranged in a matrix, i.e. voxel digital matrix. Digital information in the voxel digital matrix is converted to blocks with different grays from black to white, which are known as pixels in two-dimensional projection (Pixel), and the blocks are arranged according to a segment mode to constitute a CT image.
Existing medical CT imaging system was launched in 1972, its inventor won the Nobel Prize. In more than 40 years of application practice, CT technology constantly develops and upgrades (details are shown in FIG. 1, wherein A stands for a first generation CT, B for a second generation CT, C for a third generation CT using a fan beam detector and ray source mechanical rotation, D for a fourth generation CT with an x-ray ball tube and a mechanical rotating generator, E for a fifth generation CT of electron beam rotating, and F for a stationary real-time CT imaging system illustrated as the present invention that uses pencil beam (also known as narrow beam) x-ray sequentially emitting in parallel. For example, early CT imaging system consisting of single-photon-counting detectors and narrow-beam source scans in parallel in varied angles with parallel beams to get data for reconstruction, and then reconstructs three dimensional data through reconstruction algorithm such as Radon Transform. However, such a CT imaging system has low utilization of x-ray, long scan time, poor reconstruction image quality. Later, fan beam CT imaging system with rotation scan is launched. As shown in FIG. 2, the fan-beam CT imaging system includes a plurality of x-ray detectors arranged in an arc and a plurality of x-ray sources with big fan-angle divergent, can envelope a full slice of a person in one time, through a 360-degree scan, to complete one slice image reconstruction, thereby greatly speeding up the imaging process. In recent years, a cone-beam CT imaging system appears. The cone-beam CT imaging system uses detectors in plane array instead of those in linear array, using cone-beam scanning instead of fan-beam scanning, so that x-ray utility becomes more efficient, scanning time turns to be shorter, uniform in all directions and high precision spatial resolution are achieved. However, cone-beam CT imaging system has serious imaging scattering. Therefore, smaller pixels hardly bring fan-beam CT imaging system the same signal to noise ratio, which is the main bottleneck to improve image quality. So, the fan-beam CT imaging system applies mainly at present in small parts of the body.
As x-ray detector continues to be improved, multi-array CT detector including a plurality of x-ray units in a larger fan-angle, can collect 64-row-320-row and even more data in one rotation. In order to get more absorption characteristics of a body, the CT imaging system using multiple-energy x-ray sources to obtain body tissues' x-ray absorption data so as to obtain CT images with energy calibration. However, the existing CT imaging system for imaging still fast enough, there are motion artifacts and other issues. In clinical work, for example, a full heart image reconstructed in a rotation cycle requires CT rotation speeds up to 2 circles per second or even faster. Unfortunately, x-ray sources and x-ray detectors set at high speed rotating frame rotating 2 circles per second or even faster, cause x-ray source, high voltage generators and other assembles to work under the centrifugal force, therefore it turns to be a manufacturing technology bottleneck.
According to Chinese patent application No. CN102793554A, Siemens Company proposes a dual-source CT system having two detectors located in angles staggered from each other. In the dual-source CT system, one detector has a set of integral detector units, and the other detector has a set of counting detector units. On one hand, referring to FIGS. 3A and 3B, at the time of measuring x-ray intensity, integration of amplified electric signals is taken as signal data at this angle. The electric signals are received time intervals during which the detectors rapidly rotate a slight displacement. Because detector pixels signals are integration of the electric signals during a slight displacement, the spatial resolution encounters a bottleneck in a state of high speed rotation, and becomes conflict with rotation speed. The faster the rotation is, the greater the displacement of the pixels in unit time. Thus, signals at different locations crosstalk and overlap (that is, motion trail) more severely. The other hand, the detector has more and more layers, x-ray beams from a x-ray source are wider and wider, x-ray scattering is more and more serious, resulting in the CT images become blurred. In addition, dual-source CT system causes bodies exposed to x-ray two times or exposed to double amount x-ray at one time. Consequently, radiation exposure becomes higher and higher to go far beyond the maximum safe dose for one year.
In addition, the x-ray detectors used in the conventional technologies and those used in the fan-beam multi-slice spiral CT work in an energy integral model. This kind of x-ray detectors cannot distinguish between each x photon spectrum, thus losing energy spectrum information. But, the energy spectrum information is especially important for clinical image interpretation.